In the use of idler rollers it is known to have an idler roller system consisting of a fixed shaft having an idler roller rotatably mounted thereto, with an interposed bearing which facilitates the rotation of the idler roller about the shaft. It is also known to provide labyrinth seals for idler rollers. This combination of idler rollers and labyrinth seals is used, for example, with conveyor belts in mining and other operations. Labyrinth seals employ a tortuous network of passages between the contaminating environment and the idler roller bearing assembly. Contaminants can only infiltrate the bearing assembly by transversing the tortuous path. Idler roller failure is often caused by airborne moisture passing through the labyrinth seals.
During operation the temperature of an idler roller increases, for example, due to friction caused by a conveyor belt moving across the idler roller. This increase in temperature causes air inside the roller to expand and be expelled through the labyrinth seals. Thereafter, when the temperature of the roller decreases, the air inside the idler roller contracts. The air outside the idler roller is then drawn back inside the idler roller through the labyrinth seal. This air that is drawn into the idler roller contains moisture and contaminants which cause corrosion and damage to the bearings and races within the idler roller.
What is needed is a labyrinth seal that will allow air in the interior of the idler roller to exit the idler roller through the labyrinth seal but prevent air exterior to the idler roller from entering the interior of the idler roller through the labyrinth seal.